Well I have them going pretty quick now. About 5.5k steps/sec. That seems to be max for my motors when quarter stepping. I haven’t been having any problems when moving them fast like this. The problems come when I try to step at very low speeds. That’s when the rhythmic skipping happens. But Ive come to the conclusion hat this is because the IC is going into thermal shutdown. When running at lower speeds the IC sinks more current than the stepper and gets really hot because of this. If i actually blow on the IC to cool it off the skipping will stop. When I stop blowing it runs till it gets hot and starts skipping again. I’m wondering if I have a bad connection between the ground pad on the bottom of the IC and the copper on the board.
I wish the the chip gave some sort of pin signal indication when its shutdown down because of temp so I would know for sure.